World's first nuclear clock to probe fine-structure constant change

A team of researchers at Vienna University of Technology (TU Wien) has demonstrated that the world’s first nuclear clock, developed in 2024 using thorium nuclear transition technology, can be used to test whether the fine-structure constant changes over time. The fine-structure constant, approximately 1/137, is a fundamental dimensionless value that quantifies the strength of electromagnetic interactions, governing how light interacts with matter and influencing the forces that hold atoms together. If this constant were found to vary, it would challenge the long-held assumption that the laws of physics are fixed and universal. Unlike traditional atomic clocks that rely on electron behavior, the nuclear clock measures energy transitions within the atomic nucleus itself. The thorium nucleus shifts between two energy states, altering its shape and the distribution of its electric field, particularly its quadrupole component, which depends directly on the fine-structure constant. By precisely measuring these transitions in thorium-containing crystals, the researchers achieved a sensitivity to variations in the fine-structure